It has long been known that a vacuum is a good insulator. Accordingly, vacuum insulation panels are useful in a variety of insulation environments. While vacuum insulation panels can be quite desirable, they can be expensive to prepare. In particular, there are difficulties and relatively high costs associated with the creation of the vacuum and in forming the physical shape of the container. For example, U.S. Pat. No. 5,107,649 discloses an insulation panel comprising two bendable metal wall sheets and spacers therebetween, wherein the metal sheets are welded together and a vacuum is formed therewithin.
In order to avoid the difficulties associated with the preparation of vacuum insulation panels of the foregoing type, attempts have been made at preparing vacuum panels that are self-evacuating, i.e., that do not involve the need to create a vacuum at the time the insulation panel is produced, but rather involve the formation of a vacuum in situ at the time the insulation panel becomes cold by contacting a cold source. For example, U.S. Pat. No. 3,812,886 discloses an insulating sleeve with a perlite core that is sealed in an envelope which is filled with a condensible gas such as carbon dioxide. When the insulating sleeve becomes cold by being positioned near a cold source, the carbon dioxide condenses, thereby establishing an insulating vacuum. Similarly, U.S. Pat. No. 5,160,769 discloses an insulating enclosure comprising a foamed material containing carbon dioxide-filled cells. When the insulating enclosure becomes cold by contacting a sufficiently cold source, the carbon dioxide solidifies, thereby establishing an insulating vacuum.
While self-evacuating vacuum insulation panels have been previously described, there remains a need for an improved self-evacuating vacuum insulation panel and a method of preparing same. The present invention provides such a self-evacuating vacuum insulation panel and method of preparing same. In particular, the present inventive insulation panel can provide a greater vacuum under similar preparation and use conditions than conventional self-evacuating insulation panels. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.